Karst bauxites are valuable terrestrial records of paleoclimate and tectonic evolution formed under tropical to subtropical conditions during the subaerial exposure of carbonate platforms. This study explores Croatian bauxite deposits within the Adriatic–Dinaric Carbonate Platform (ADCP), with a focus on the distribution and enrichment of rare earth elements (REE) across eight bauxite horizons from the Triassic to Neogene periods. The research applies statistical analyses of geochemical data, as well as developed models, to assess the factors influencing REE distribution and fractionation. The study found that variations in parent material, along with changes in paleogeographical and paleotectonic settings, significantly affected the REE content. The median REE concentrations in the analyzed bauxite horizons range from approximately 250 to 570 mg/kg. Notable REE enrichment was observed in the Late Paleogene, particularly in the Middle and Upper Eocene horizons. The analysis highlights the importance of physicochemical conditions, such as Eh and pH, during the weathering processes that lead to bauxite formation. The results suggest that the presence of REE-bearing minerals, rather than clay minerals, could possibly contribute to elevated concentrations of heavy REE (HREE). These findings indicate that Croatian bauxites, enriched in REE and associated trace elements, are significant not only as geological markers of past climatic and tectonic events but also as potential sources of critical raw materials. This study underscores the potential for the economic exploitation of these deposits in the context of modern technological demands.

Karst bauxites represent important archives of paleoenvironmental conditions and potential sources of REE and other critical raw materials (CRMs). This study presents a multiproxy investigation of the Upper Eocene Mamutovac-1a bauxite deposit (Croatian Dinarides), integrating petrography, X-ray diffraction (XRD), magnetic susceptibility, whole-rock geochemistry, and aqua regia extractions along a 25.1 m drill core. The deposit shows clear vertical variability defined by four facies-based zones, accompanied by systematic mineralogical and geochemical changes. The bauxite is dominated by böhmite, gibbsite, hematite, and anatase, with subordinate goethite and clay minerals. ΣREE concentrations range from 276 to 670 mg/kg and increase toward the deeper zones, with consistent LREE enrichment relative to HREE, negative Eu anomalies, and variable Ce anomalies. Correlations suggest that REE are likely associated with phosphate phases, with a possible secondary contribution from clay minerals. The integrated dataset indicates a polygenetic, multi-stage evolution involving both in situ bauxitization and episodic reworking and redeposition, controlled by variable redox conditions and fluid–rock interaction. Geochemical signatures suggest a mixed provenance with contributions from intermediate to ultramafic sources. The elevated concentrations and enhanced extractability of selected elements (La, Sc, Ga, V) indicate that the deposit may represent a potential secondary source of CRMs.